The present invention relates to an auto-leveling system for vehicle headlamp that tilts and adjusts automatically an optical axis of a headlamp based on an inclination of a vehicle in the longitudinal direction (referred to as a “pitch angle” hereinafter) in the direction to offset the inclination by an angle equivalent to on the pitch angle (referred to as an “auto-leveling” hereinafter) and, more particularly, a auto-leveling system for vehicle headlamp that is effective for the vehicle equipped with a daytime running light that is turned on even in the daytime to inform other running vehicle and the walker that such vehicle is running.
In the headlamp of this type, for example, a reflector to which a light source is fitted is supported on a lamp body tiltably round a horizontal tilt axis, and also an optical axis of the reflector (headlamp) can be tilted round the horizontal tilt axis by the actuator.
Then, the conventional auto-leveling system is constructed by providing the control portion that controls a drive of the actuator based on sensed signals of a pitch angle sensing means, a peed sensor, etc. to the vehicle. The control portion adjusts the optical axis of the reflector such that the optical axis of the reflector is always set in a predetermined state with respect to the road surface (auto-leveling) when a headlamp lighting switch is in its ON state.
However, in some countries in North America and Northern Europe, the law obligates to equip the daytime running light, which is turned on even in the daytime to inform other running vehicle and the walker that such vehicle is running, as one means of the measure for safety. Then, as modes of the daytime running light, there are the case where a dipped beam of the headlamp is utilized and the case where a main beam that is dimmed not to form a glare light is utilized. In both cases, the headlamp is caused to turn on.
Hence, if the conventional auto-leveling system, which is applied to the daytime running light unequipped vehicle, is applied to the daytime running light equipped vehicle as it is, the auto-leveling system that should not be operated is also operated since the headlamp is turned on (a headlamp lighting switch is set to its ON state) even in the daytime. As a result, because an operating frequency of an actuator is increased, an amount of power consumption is increased and also a lifetime of the actuator is shortened in contrast to the daytime running light unequipped vehicle. It is of course that, if a motor with great durability is employed, the lifetime of the actuator is lengthened. But there is caused such problems that the motor is large in size and expensive and also the headlamp is increased in size.